1. Technical Field
The present invention relates to a polarizing plate protective film, a polarizing plate, an image display device, and a method of manufacturing the polarizing plate protective film.
2. Background Art
In recent years, a liquid crystal display device has been widely used in applications such as a liquid crystal panel of a liquid crystal television, a personal computer, a mobile phone, a digital camera, and the like. In general, the liquid crystal display device has a liquid crystal panel member in which polarizing plates are formed at both sides of a liquid crystal cell, and performs a display by controlling a light from a backlight member by the liquid crystal panel member. The polarizing plate includes a polarizer and its protective film (polarizing plate protective film). A general polarizer is obtained by stretching a polyvinyl alcohol (PVA)-based film stained with an iodine or dichroic dye. As for the protective film, for example, a cellulose acylate film or the like has been used.
While the quality of a recent liquid crystal display device has been enhanced, the applications are diversified, and a demand for durability is becoming strict. In view of durability, for example, stability against environmental changes is required in use in outdoor applications, and in a polarizing plate, it is required to suppress a change of optical characteristics with respect to temperature or humidity changes.
In Japanese Patent Laid-Open Publication No. 2006-083225 (hereinafter referred to as “JP-A-2006-083225”), it has been studied that a film with a low moisture permeability (a low moisture permeability film) is used as a polarizing plate protective film to suppress a deterioration of a polarization performance of a polarizing plate under conditions of high temperature and high humidity. More specifically, JP-A-2006-083225 discloses a film having a cured layer obtained by coating a curable composition on a transparent substrate film and curing the composition, the curable composition containing a compound having a specific cyclic aliphatic hydrocarbon group, and two unsaturated double bond groups in a molecule.
The film disclosed in JP-A-2006-083225 is, particularly, a polarizing plate protective film disposed on the outermost surface at the viewing side of an image display device, and has an excellent hardness, and a predetermined (about 320 g/m2/day) low moisture permeability. However, the inventors of the present invention have conducted studies in order to achieve both a further reduction of a moisture permeability, and a hardness.
Accordingly, an object of the present invention is to provide a polarizing plate protective film with a high hardness and a low moisture permeability.
Another object of the present invention is to provide a polarizing plate having the polarizing plate protective film, an image display device, and a method of manufacturing the polarizing plate protective film.